This document proposes a grid interfacing scheme for a hybrid renewable energy system combining photovoltaic (PV) and permanent magnet synchronous generator (PMSG) wind energy. It describes a system where the outputs of the PV array and wind turbine are connected to a common DC bus and then to an inverter. A hysteresis current controller is used to synchronize the inverter output to the grid frequency and voltage. Simulation results show the DC input from the hybrid source, inverter output voltages, grid injected voltages and currents, and grid voltage ratings. The document concludes the hysteresis current control method provides fast response without requiring feedback compensation and can adapt to variable switching frequencies.

1. 2004 http://ijesc.org/
DOI 10.4010/2015.489
ISSN2321 3361 © 2015 IJESC
A Grid Interfacing Scheme for PV and PMSG Based Wind Energy
System
Vasudevan r1
, Dr. N. Yadaiah2
Professor and Registrar2
Department of Electrical & Electronics Engineering
JNTU University college of Engineering
Vasudevan1101@gmail.com1
, yadaiah.n@jntuh.ac.in2
Abstract:
Renewable vitality based appropriated era frameworks assume a prevailing part in power creation with the increment in force
request. Conveyed era in view of renewable vitality sources, for example, wind, sun powered vitality can be utilized as an option
by interconnecting to the miniaturized scale matrix. In this paper we propose "Renewable Sources Grid Interfacing System" for
compelling protection of renewable vitality assets. We abuse different vitality sources in the meantime suggesting burden
sharing standard, this examination investigates the parts of Load Sharing wonder of a framework associated Renewable Energy
System (RES). In our model sun oriented and wind vitality sources have been considered. The procured results delineate that the
execution can be enhanced by changing the stage edge and adjustment file of network inverter. Thus Renewable vitality sources,
for example, sun based and wind vitality can assume a critical part in taking out the vitality emergency in our nation if used
appropriately. The vast majority of the renewable vitality frameworks are worked in stand-alone mode, which just supply energy
to settled burdens. Interconnection of this framework with utility is the present outline pattern.
Keywords: Photo voltaic, PMSG, HCC, grid connection
I.INTRODUCTION
Vitality request all through the world has been expanding
quickly. The present vitality sources, for example, oil
stores, coal stores, characteristic gas are modest and getting
restricted in supply. Along these lines, there is a dire need
to preserve accessible assets and use vitality however much
as could reasonably be expected, joined wind-PV half and
half - era framework uses the sunlight based and twists
assets for Electric Power Generation. Individual wind and
sun oriented renewable sources have eccentric irregular
conduct. As for the duration of the day sun based vitality is
available however because of the sun force and capricious
shadows by the mists, flying creatures, trees and so forth
the sun powered light levels fluctuates. Because of this
reason sunlight based vitality is untrustworthy and less
utilized.
Because of the uneven warming of the air by the sun wind
stream, because of the earth territories, waterways and
vegetation the wind stream examples are adjusted. Wind
turbine changes over the motor vitality in the wind into
mechanical then to electrical by turning the generator which
is associated inside. Wind is exceptionally eccentric
arbitrary conduct, yet it is fit for supplying substantial
measure of force. Because of this idea wind vitality is
problematic and less utilized. So it is ideal to utilize half
breed era framework which is superior to anything
individual wind or individual PV era framework. So it is
conquer the faults of individual framework. Network
interface of half breed era framework enhances the
framework unwavering quality.
Fig 1 block diagram
Fig 2 Circuit diagram of proposed RES with HCC
In this framework there is a wind's turbine, the wind yield
turbine goes to Permanent Magnet Synchronous Generator.
Research Article December 2015 Issue

2. 2005 http://ijesc.org/
The wind's yield framework is in AC so we require AC to
DC converter to change over the AC yield into DC. So also
in the PV side the yield of the PV cluster is associated with
a dc-dc support converter to raise the yield voltage up to a
longing level. The yield of PV and wind are associated with
a typical DC join voltage. The normal DC join voltage will
be associated with the DC to AC converter and the
inverter's yield is synchronizing with framework. This
inverter changes DC power from PV exhibit and the wind
turbine into AC force and it keep up the voltage and
recurrence is equivalent to the framework voltage and
recurrence keeping up Synchronism in Operation.
II. MICRO GRID
A micro grid consists of cluster of loads and distributed
generators that operate as a single controllable system. As
an integrated energy delivery system micro grid can be
operated in parallel or in isolated mode with the main
power grid in order to meet the required power demand.
Photovoltaic system, wind turbine generator are used for
development of a micro grid.
There are always changes in the condition of weather and
speed of wind. Wind and solar system are condition
dependents, i.e. the operating parameters changes according
to the weather conditions and are unpredictable. Hence a
control module is required to predict the speed of the wind
and sunlight conditions for solar cell accurately. The
control of voltage and frequency is necessary in grid
connected mode because the fluctuations in frequency and
voltage on the transmission in a transmission line vary in
seconds to minutes time scale. If any one of these
parameters are left unchecked it could damage the system
as well as equipment used in the grid.
In this work, Hysteresis current controller is employed to
achieve active synchronization i.e. matching the phase and
frequency with the grid. This control technique is most
reliable amongst other control techniques such as pulse
width modulation (PWM) voltage mode control, pulse
width modulation (PWM) current mode control with
proportional (P), proportional integral (PI) and proportional
integral derivative (PID) controllers. These conventional
control methods like P, PI, and PID are uncontrollable for
large parameter and load variations. Therefore non-linear
controllers were employed for controlling grid parameter
variations. The non-linear controllers have ability to react
suddenly to a transient condition. The hysteresis controller
is one such non-linear controller which has been employed
because of its fast response with simple design and
implementation, react immediately for the load transients
and does not require feedback loop compensation and its
adaptability to variable switching frequency operations.
The current hysteresis control incorporates the advantages
of both hysteresis control and current mode control. It can
be implemented using two loop control method i.e. the
actual grid current is measured and compared with the
reference current, pulses to the inverter are generated
according to the error between actual and grid currents, the
phase lead between the grid and inverter voltages required
for power transfer is achieved by matching the phase and
frequency.
For the wind generation system, small-scale vertical axis
wind turbines (VAWTs) are employed due to their ability
to capture wind from different directions without using a
yaw. The main problem associated with these vertical axis
wind turbines is over-speeding and component overloading
at excessive wind velocities producing voltage and
frequency fluctuations. The hysteresis current controller
employed smooth out the fluctuations sacrificing the peak
power point tracking capability. For the PV generation
system, hill climbing technique is employed to extract
maximum power from the PV panel. This technique gives
guidelines for designing perturb magnitude and time
interval between perturbations to improve the maximum
power point tracking efficiency. The voltage source inverter
(VSI) transfers the energy drawn from the wind turbine and
PV array to interface with the grid and HCC method
developed synchronizes phase of the voltages and
frequency with the grid. The design and development are
carried out in mat lab/Simulink environment.
III. CONTROL STRATEGY
Various methods of gridinterfacing and control of RES
based generation systems arediscussed in I2, 3 and 4].
Hysteresis Current Control (HCC) isone such method.
Digital implementation of the controlschemes using micro
controllers has been a significantdevelopment in the recent
past. HCC is easy for digitalimplementation. Control
schemes using HCC are proposedand discussed elaborately
in I5, 14]. Simple programming ofthe logic in C language is
all that is required. This paperpresents how HCC can be
implemented digitally in a simplerway. The transfer of
power into the grid is achieved withoutusing a PI controller.
In HCC the inverter output current is forced to follow
thegrid voltage in terms of the time phase. The advantage
of themethod is that the preliminary conditions to be
satisfied inorder to achieve synchronization is fulfilled by
default; that is,matching the phase and the frequency
happens by default I12].
The phase lead between the grid and the inverter
voltages,required for power transfer is also achieved by
default. Thismakes this control scheme the most reliable
among othercontrol methods. In our proposed control
strategy the RES is connected to avoltage source inverter
(VSI) as a DC source. If the RESgenerates AC voltage, that
can be connected to the VSI afterrectifying it. The DC link
capacitor acts as an isolator inbetween the converters (the
rectifier and the inverter)providing the freedom for
independent control of both theconverters. The power from
some of the less stable RESshould be conditioned before
connecting them to the VSI. Thebasic aspect of the control
strategy has been discussed in I5].The DC link (transfers
the power from the RES to the grid. Thecontrol scheme is
shown in Fig 1.

3. 2006 http://ijesc.org/
The inverter output current, in this control scheme, isforced
to follow the grid voltage. The grid voltage isconverted to a
unit vector template using a unity sine wavegenerator
(basically an op-amp circuit designed for less thanunity
gain) and then this waveform is used as the
referencecurrent. The actual grid current is measured and
comparedwith the reference current which is the unit sine
wave obtainedfrom the grid, and the pulses are generated
according to theerror between the actual current and the
grid current [8, 15].
The unity vector templates are obtained from the
gridvoltage, here the synchronizing angle, tklf the three
phases isused to force the inverter output current to follow
the gridvoltage. The unit vector templates are represented
as
Ua=sin(θ) (1)
Ub=sin(θ-2π/3) (2)
Uc=sin(θ+2π/3) (3)
These unit vector templates are sampled and fed to
themicrocontroller and compared with the actual grid
currents la,Ib and Ie sampled from the grid directly.
Ia>= (Ua +h) (4)
Ib>= (Ub +h) (5)
Ic>= (Uc +h) (6)
where, h is the hysteresis band provided. If all the
threeconditions of equations (4), (5) and (6) are satisfied
then theupper switches of the three phase inverter are
switched on.
Ia< (Ua-h) (7)
Ib< (Ub-h) (8)
Ic< (Uc-h) (9)
If the three conditions of equations (7), (8) and (9)
aresatisfied, then the upper switches will be switched off
and thelower switches will be switched on.
In order to synchronize the RES to the grid the
magnitude,the frequency and the phase of the voltages on
the two sidesshould match [6]. The control scheme
presented here easilymanages these aspects. The reference
current is obtained fromthe grid voltage. This helps the
control scheme to generateswitching pulses for the inverter
such that the inverter outputcurrent is in the same phase and
frequency as that of the grid voltage. Apart from the
synchronization, the inverter output voltageshould lead the
grid voltage in order to achieve power transferfrom the
RES to the grid. As far as this control scheme isconcerned
the inverter output current is of the same phase asthat of the
grid current and also lags the inverter outputvoltage by an
angle decided by the inductance in the circuit.
Thus by default the inverter output voltage leads the
gridvoltage by the same angle. This makes the power
transfer tothe gird possible [11].
The control scheme using these equations thus
providesswitching pulses to the inverter in such a way that
the inverteroutput current is forced to follow the reference
current strictly.
IV. SIMULATION RESULTS
Simulation is performed using
MATLAB/SIMULINK software. Simulink liabrary files
include inbuilt models of many electrical and electronics
components and devices such as diodes, MOSFETS,
capacitors, inductors, motors, power supplies and so on.
The circuit components are connected as per design without
error, parameters of all components are configured as per
requirement and simulation is performed.
SIMULATION CIRCUIT:
GRID MODEL:
HYBRID SOURCE:

4. 2007 http://ijesc.org/
WAVEFORMS:
a) DC input from hybrid source
b) Inverter output voltage
c) Grid injected voltages:
d) Grid injected currents:
e) Grid voltage ratings:
REFERENCES
[1] F. Blaabjerg, R. Teodorescu, M. Liserre, and A. V.
Timbus, "Overview of control and grid synchronization for
distributed power generation systems," IEEE Trans. Ind.
Electron., vol. 53, no. 5, pp. 1398-1409,Oct.2006.
[2] G. Tapia, G. Santamaria, M. Telleria and A.
Susperregui,"Methodologyfor Smooth Connection of
Doubly Fed InductionGenerators to the Grid,"IEEE Trans
.on Energy Conversion, vo1.24, no. 4, Dec. 2009.
[3] N. Joshi and Ned Mohan, "A Novel Scheme to Connect
Wind Turbinesto the Power Grid," IEEE Trans. on Energy
Conversion, vol. 24, no. 2,june. 2009.
[4] S. Z. Chen, N. C. Cheung, Y. Zhang, M. Zhang, and X.
M.Tang,"Improved Grid Synchronization Control of
Doubly Fed InductionGenerator Under Unbalanced Grid
Voltage," IEEE trans onEnergyConversion, vol. 26, no. 3,
sept. 2011.
[5] M. Singh" V. Khadkikar" A. Chandra" and R. K.
Varma" "GridInterconnection of Renewable Energy
Sources at the Distribution LevelWith Power-Quality
Improvement Features," IEEE trans on powerdelivery, vol.
26, no. I, jan. 20 II.
[6] T. Abeyasekera, C. M. Johnson, Member, D. 1.
Atkinson and M.Armstrong "Suppression of Line Voltage
Related Distortion in CurrentControlled Grid Connected
Inverters" IEEE Trans., Power Electron,vol. 20, no. 6, pp.
1393-1401, Nov 2005.
[7] E. Twinning, "Modeling grid-connected voltage
sourceinverteroperation," in Proc. AUPEC'01, 2001, pp.
501-506.
[8] E. Twinning and D. G. Holmes, "Grid current regulation
of athree-phasevoltage source inverter with an LCL input
filter," IEEE Trans.PowerElectronics, vol. 18, no. 3, pp.
888-895, May 2003.
[9] N. Mohan, T. M. Underland, andW. P. Robbins, "Power
Electronics,Converters, Applications, and Design". New
York: Wiley, 1989.
[10] V. Khadkikar, A. Chandra, A. O. Barry, and T. D.
Nguyen, "Applicationof UPQC to protect a sensitive load
on a polluted distribution network,"in Proc. Annu. Con!
IEEE Power Eng. Soc. Gen. Meeting, 2006, pp.867-872.
[11] M. Singh and A. Chandra, "Power maximization and
voltage sag/swellride-through capability of PMSG based
variable speed wind energyconversion system," in Proc.
IEEE 34th Annual. Coni Indus.Electron.Soc., 2008, pp.
2206-2211.
[12] P. Rodriguez, J. Pou, J. Bergas, J. I. Candela, R. P.
Burgos, andD.Boroyevich, "Decoupled double synchronous
reference frame PLL forpower converters control," IEEE
Trans. Power Electron, vol. 22, no. 2,pp. 584-592, Mar.
2007.
[13] Recommended Practice fin' Utility Interface or
Photovoltaic(PV)Systems, IEEE Std. P929, Dec. 1998.

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[l4] M. Mohseni, S. M. Islam and M. A. S. Masoum,
"Enhanced Hysteresis BasedCurrent Regulators in vector
control o{ DFIG wind turbines ,"IEEE Trans. Power
Electronics, vol. 26, no. 1, pp. 223-233, Jan 2011.
[l5] A. Timbus, M. Lisere, R. Teodorescu, P. Rodriguez
and F. BZaabjerg, "Evaluation o{ Current Controllers ./br
Distributed Power Generation Systems," IEEE Trans.
Power Electronics, vol. 24, no. 3, pp. 654-663,March 2009.
Student Profile:
Vasudevan.R, Recently he was completed M.Tech (PEID)
from EEE Department in JNTU University college of
Engineering, Hyderabad, India.